U.S. patent number 5,651,193 [Application Number 08/193,710] was granted by the patent office on 1997-07-29 for grain dryer and control system therefor.
This patent grant is currently assigned to The GSI Group, Inc.. Invention is credited to Victor D. Goeckner, Timothy P. McDonough, Cloyce Newton, Virgil O. Rhodes, Gary Woodruff.
United States Patent |
5,651,193 |
Rhodes , et al. |
July 29, 1997 |
Grain dryer and control system therefor
Abstract
A grain dryer for providing a controlled drying process through
a housing. The housing has a path for grain to be dried such that
the grain is dried as the grain moves along the path. The grain
dryer also has a fan and heater assembly for supplying heated air
to the path for drying grain in the path. The grain dryer can
control the flow of grain along said path and has sensors disposed
in predetermined positions so as to detect different fault
conditions. The sensors generating corresponding fault signals in
response to the detection of fault conditions. The grain dryer also
has a controller operatively connected to the sensors, the
controller is responsive to fault signals to initiate a
predetermined shutdown procedure upon receipt of any one of the
fault signals. A memory is operatively connected to the controller
for electronically recording and identifying information concerning
shutdown procedures initiated by the controller. The grain dryer
controller controls the start-up of in a predetermined manner. The
grain dryer includes a memory to store identifying information in
memory for a predetermined number of shutdowns initiated by the
controller.
Inventors: |
Rhodes; Virgil O. (Ramsey,
IL), McDonough; Timothy P. (Springfield, IL), Newton;
Cloyce (Diveron, IL), Goeckner; Victor D. (Auburn,
IL), Woodruff; Gary (Frankfort, IN) |
Assignee: |
The GSI Group, Inc.
(Assumption, IL)
|
Family
ID: |
22714719 |
Appl.
No.: |
08/193,710 |
Filed: |
February 9, 1994 |
Current U.S.
Class: |
34/531; 34/535;
34/562; 34/572 |
Current CPC
Class: |
F26B
17/122 (20130101); F26B 25/009 (20130101) |
Current International
Class: |
F26B
17/12 (20060101); F26B 25/00 (20060101); F26B
013/10 () |
Field of
Search: |
;34/526,531,535,544,562,563,564,572 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Moridge Grain Dryers Models 8330. 8440. .
Farm Fans -Move Grain By Air Convey. Air. .
Farm Fans -Staged Automatics "Temper. Dry" Grain. .
Farm Fans -Automatic Grain Dryers. .
Farm Fans. Full Heat Drying CF Series. .
American Farm Equipment Co. American Automated Grain Dryers Models
1503T-1706T. .
American Farm Equipment Co. American Electronic -Annunciator. .
GT Model Rab-5000 Recirculating Automatic Batch Dryer 1987 GT, Inc.
.
Mathews Company Expandable Continous Grain Dryer D-2119.2.87. .
Mathews Company-Models 670-970 Grain Dryers D-2068-7.86. .
Mathews Company -Model 375 Grain Dryer Portable Electric Drive
Continuous Plow Jul. 1986. .
Airstream-Modular Stack Dryer AS01-2.91..
|
Primary Examiner: Sollecito; John M.
Assistant Examiner: Gravini; Steve
Attorney, Agent or Firm: Polster, Lieder, Woodruff &
Lucchesi
Claims
What is claimed is:
1. A grain dryer comprising:
a housing defining a path for grain to be dried;
a fan and heater assembly for supplying heated air to the path for
drying grain the path;
a plurality of sensors for sensing different fault conditions, at
least one of said sensors being disposed to detect airflow from the
fan and heater assembly;
control means responsive to the sensor for controlling operation of
the fan and heater assembly to initiate a shutdown procedure upon
the indication of a fault condition, said control means being
responsive to the airflow sensor to initiate the shutdown procedure
only when the indication of an airflow fault condition continues
for a predetermined time.
2. The grain dryer as set forth in claim 1 wherein the
predetermined time is approximately two seconds.
3. A grain dryer comprising:
a housing defining a path for grain to be dried;
a fan and heater assembly for supplying heated air to the path for
drying grain in the path, said fan and heater assembly having a fan
and a heater, said fan being operable independently of the
heater;
a plurality of sensor for sensing different fault condition, at
lease one of said sensors being disposed to detect airflow from the
fan and heater assembly;
control means for controlling operation of the fan and heater
assembly, said control means being responsive to the sensor to
initiate a shutdown procedure upon the indication of a fault
condition, said control means being responsive to the airflow
sensor to start the fan only when the airflow sensor indicates no
airflow from the fan and heater assembly, said control means being
further responsive to the airflow sensor to start the heater only
if the airflow sensor indicates the flow of air from the fan and
heater assembly within a predetermined length of time after the fan
is started.
4. The grain dryer as set forth in claim 3 wherein the
predetermined length of time is approximately twenty seconds.
5. The grain dryer as set forth in claim 3 wherein the control
means initiates the shutdown procedure if the airflow sensor
indicates lack of airflow from the fan and heater assembly before
the fan is started.
6. The grain dryer as set forth in claim 3 wherein the control
means initiates the shutdown procedure if the airflow sensor
indicates lack of airflow from the fan and heater assembly within
the predetermined length of time after the fan is started.
7. A grain dryer system comprising:
a housing defining a path for grain to be dried;
a fan and heater assembly for supplying heated air to the path for
drying grain in the path;
means for controlling the flow of grain out of the housing;
means for sensing fault conditions associated with the drying of
the grain;
a controller operatively connected to the sensing means for
controlling operation of the dryer and for initiating shutdown
procedures in response to fault condition; and
means for communicating identifying information concerning fault
conditions between the controller and a site remote from the dryer,
wherein the communicating means includes telecommunications means
for communicating with the remote site via telephone lines.
8. A grain dryer comprising:
a housing defining a path for grain to be dried such that said
grain is dried as the grain moves along said path;
a fan and heater assembly for supplying heated air to the path for
drying grain in the path;
means for controlling the flow of grain along said path;
a plurality of sensors disposed in predetermined positions so as to
detect a plurality of different fault conditions, said sensors
generating a plurality of corresponding fault signals in response
to the detection of said fault conditions;
a controller operatively connected to the sensors, said controller
being responsive to said fault signals to initiate a predetermined
shutdown procedure upon receipt of any one of said fault
signals;
a memory operatively connected to said controller for
electronically recording identifying information concerning
shutdown procedures initiated by the controller; and
said controller having means for controlling start-up of said dryer
in a predetermined manner.
9. The grain dryer as set forth in claim 8 wherein the identifying
information recorded in the memory includes the identity of the
sensor which detected a fault condition.
10. The grain dryer as set forth in claim 8 wherein the controller
includes a clock and wherein said identifying information recorded
in the memory includes the time at which the corresponding fault
signal occurred.
11. The grain dryer as set forth in claim 8 wherein the controller
includes means for controlling the memory to store identifying
information in memory for a predetermined number of shutdowns
initiated by the controller.
12. The grain dryer as set forth in claim 11 wherein the means for
controlling the memory is under programmed control to keep the
identifying information for the most recent shutdowns initiated by
the controller.
13. The grain dryer as set forth in claim 8 wherein the memory
includes a battery associated therewith to maintain the contents of
the memory irrespective of whether external power is provided to
the dryer.
14. The grain dryer as set forth in claim 8 further including a
display device for displaying identifying information relating to
shutdowns irrespective of whether the dryer is in operation.
15. The grain dryer as set forth in claim 8 wherein the identifying
information stored in the memory for each different fault condition
is unique.
16. The grain dryer as set forth in claim 15 wherein the unique
identifying information is preprogrammed into the controller, said
controller in response to receipt of a particular fault signal
causing the corresponding unique identifying information to be
stored in the memory.
17. The grain dryer as set forth in claim 8 wherein the controller
is a computer under programmed control, further including a
hardware timer independent of the computer for shutting down
operation of the dryer after expiration of a predetermined time
after receipt of any one of said fault signals irrespective of any
action taken by said computer in response to said fault signal.
18. The grain dryer as set forth in claim 8 further including
interface means for accepting fault signals from equipment external
to the housing, said controller being responsive to said external
equipment fault signals to initiate said predetermined shutdown
procedure and to record corresponding identifying information in
the memory.
19. The grain dryer as set forth in claim 18 wherein said
corresponding identifying information indicates that the shutdown
was the result of a fault signal originating from outside the
dryer.
20. A grain dryer comprising:
a housing defining a path for grain to be dried;
a fan and heater assembly for supplying heated air to the path for
drying grain in the path;
transport means associated with the housing for transporting
grain;
a plurality of sensors for sensing a plurality of different fault
conditions;
control means responsive to the input signals for controlling
operation of the fan and heater assembly and the transport means to
perform a drying cycle for the grain, said control means including
a plurality of timers for measuring the time remaining in a
plurality of portions of the drying cycle, said control means being
responsive to the sensors to initiate a shut down procedure upon
receipt of a signal from said sensors indicative of a fault
condition, said control means being further responsive to receipt
of said fault condition indicating signal to store the state of
each timer so that upon a restart of the dryer the drying cycle may
resume at the point at which the fault condition occurred.
21. The grain dryer as set forth in claim 20 wherein the control
means includes a timer for keeping a running total of the time the
dryer is in actual operation, said control means being responsive
to a shutdown to stop said timer.
22. The grain dryer as set forth in claim 21 further including a
plurality of manually operable switches for providing control
information to the control means, said switches including a start
switch to provide a start signal, said control means controlling
the running total timer to begin adding time to the running total
in response to actuation of the start switch only.
23. The grain dryer as set forth in claim 20 wherein the control
means timers include dry, cool, and unload timers, said control
means including means responsive to the dryer being in a batch mode
of operation for obtaining a total dry time for a batch of grain by
summing the times on said dry, cool and unload timers.
24. A grain dryer comprising:
a housing defining a path for grain to be dried;
a fan and heater assembly for supplying heated air to the path for
drying grain in the path;
means for controlling the flow of grain out of the housing, said
controlling means including at least one roll disposed along said
path;
a controller operatively connected to the controlling means for
controlling operation of the roll, said roll being rotatable in
first and second directions, the controller controlling the roll to
rotate primarily in the first direction and to rotate in the second
direction on predetermined occasions, so that grain is prevented
from building up excessively around the roll.
25. The grain dryer as set forth in claim 24 wherein the controller
controls the roll to reverse direction of rotation at predetermined
times.
26. The grain dryer as set forth in claim 24 wherein the direction
of rotation of the roll is reversed for a predetermined length of
time during predetermined periods of operation of the dryer.
Description
BACKGROUND OF THE INVENTION
This invention relates to a solid state, microcontroller controller
for controlling operation of a grain dryer. The controller of the
present invention may be used with a variety of grain dryers, but
the controller of the present invention will herein be described in
conjunction with a vertical flow grain dryer that may be operated
in continuous batch, staged automatic, or continuous flow drying
modes.
Typically, such a grain dryer comprises a housing having an outer
basket of perforate construction and an inner basket also of
perforate construction with the inner basket spaced from the outer
basket a desired distance (e.g., fourteen inches) so as to form a
column of grain to be dried. The wet grain to be dried is delivered
to a horizontal garner bin at the top of the dryer. Both the inner
and outer baskets are usually concentric relative to one another
and are in the form of a vertically disposed diamond shape (when
viewed in cross section) such that wet grain from the garner bin is
split into two columns, one on each side of the inner basket, by
the upper pointed end of the inner basket such that substantially
equal quantities of grain flow down the path defined by the grain
columns on each side of the inner basket. One or more fans/heater
units at one end of the dryer forces heated air into the interior
of the inner basket such that the inner basket constitutes a drying
or plenum chamber. The heated air is distributed in the plenum
chamber and is forced through the perforate inner basket into the
grain column to dry the grain in the grain column. The air with the
moisture from the grain is discharged to the atmosphere as it
passes through the perforate outer basket.
The wet grain is loaded into a garner bin at the top of the dryer
by a loading auger or the like. A horizontal auger in the garner
bin distributes the grain horizontally such that there is a uniform
quantity of grain in the garner bin from one end of the dryer to
the other. After the grain has traveled downwardly through the
grain column and after it has been dried, the dried grain is
discharged from the bottom of the grain column. At the bottom of
the grain column, metering rolls are provided which are positively
driven so as to control the rate at which dried grain is conveyed
from the grain column. The dried grain is discharged into a
horizontal grain discharge conduit. The rate of operation of the
metering rolls controls the rate of movement of the grain through
the dryer and thus regulates the throughput of the dryer. A
discharge auger is located in the discharge conduit so as to convey
the dried grain from the dryer. The dried grain discharged from the
dryer is oftentimes deposited in a pickup well from which it is
conveyed to a holding or conditioning bin by way of another auger
conveyor.
The fan/heater assembly typically includes an axial flow fan which
forcefully draws large quantities of air into a relatively large
cylindrical housing and forces the air through the housing and into
the drying chamber. (Although the fan is preferably an axial flow
fan, centrifugal fans or other types may also be used. Similarly,
although a cylindrical housing is primarily used, other housing
shapes such as rectangular or square may also be used.) The heater
is usually a gas fired burner fueled by liquid propane or the like.
The burner is located within the cylindrical housing downstream
from the fan such that the fuel is burned within the housing and
such that the flame and the products of combustion mix with the air
flowing through the housing thereby to heat the air to a desired
temperature. In certain models of dryers, only a single fan/heater
unit is used. In other dryers, two or three fan/heater units, one
on top of the other, are employed. In modular stack dryers, two or
even three grain dryers (which need not all be identical) such as
above described are stacked vertically one on the other with the
grain from the uppermost dryer flowing directly into the grain
columns of the next lower dryer with the different dryers being
programmed to dry the grain in stages. In fact, because of the
ability of the present control system to control different models
and sizes of dryers using the same control circuitry, the dryers in
a stack can be of very different construction, size, etc. and still
be controlled by a single control circuit.
A controller for such a dryer must control operation of the inlet
and outlet augers supplying wet grain to the dryer and carrying
away dried grain. The controller must also control the operation of
the fan/heater units, the upper and lower grain augers, and the
metering rolls. The controller must monitor a number of temperature
sensors located in various locations within the dryer so as to
enable automatic operation of the dryer to dry the grain to a
desired moisture level without overheating the grain (which could
cause damage to the grain), and must shut down operation of the
dryer in the event certain parameters being monitored by the
controller are outside limits established for these parameters
corresponding to undesirable operating conditions for the
dryer.
Prior art dryer controllers typically were analog electromechanical
systems. These prior art controllers were difficult and expensive
to manufacture, were difficult to reconfigure or change to
accommodate different grain drying conditions, which oftentimes
required that components (e.g., timers) be physically replaced to
change dryer control parameters. Further, the reliability of such
electromechanical systems was not at the level that was
desired.
Prior art dryer controllers had several shortcomings. For example,
in the event a prior art dryer controller would sense a dryer
shutdown condition and would shut down the dryer, the controller
typically would have a series of indicator lights that would help
locate the source of the shutdown. However, in the event of a
shutdown, many operators would immediately attempt to re-start the
dryer. This re-start procedure would re-set all of the indicator
lights so that the operator would not know the likely source of the
shutdown (unless the operator either remembered or wrote down the
indicator light that was lit) in the event the dryer needed to be
serviced.
Prior art controllers would allow all of the motors on the dryer to
start simultaneously thus resulting in current draws that may
exceed the capability of the electric service available for the
dryer. In many dryer installations of a farm or the like, the
available electric service may only be 230 volts, single phase
power. With prior art controllers, it was necessary for the
operator to manually startup the dryer in such manner that only one
motor was started at a time to insure that the current draw for the
dryer was maintained within the capability of the electric service
available. Many operators would not follow proper startup
procedures.
Also, prior art controllers could not differentiate between safety
related shutdown conditions (e.g., a grain over temperature or
detection of a flame) and a non-critical shutdown condition (e.g.,
an out of incoming grain condition). Difficulty would oftentimes be
experienced in that shutdown of the unloading auger would result in
the auger becoming jammed, thus requiring a time consuming manual
unloading of the dryer or the unloading auger. This necessitated
considerable additional work and time required to get the dryer
back in operation after a non-critical shutdown.
It will also be appreciated that a manufacturer offering a full
line of dryers so as to serve small on-farm drying requirements and
large commercial grain storage facilities, a large number of dryer
models are necessary. For example, Grain Systems, Inc. of
Assumption, Ill. offers about sixty-two (62) models of the
above-described grain dryers. With prior art electromechanical
controllers, it was necessary to have a different controller for
every different dryer model. This presented logistical problems in
manufacturing the dryers and also present difficulties in servicing
the dryers in the field and in stocking replacement controllers for
these dryers.
SUMMARY OF THE INVENTION
Among the objects and features of the present invention may be
noted the provision of a controller for a grain dryer in which the
components are substantially all solid state and computer
controlled such that the reliability, of the controller is
increased and the ability to make changes to the operation and the
method of control of the dryer may readily and easily be carried
out as by changing the software for the microcontroller;
The provision of such a controller in which the startup of the
motors in the dryer is staged such that the motors are sequentially
started one at a time so as to minimize the current draw
requirements of the grain dryer on startup;
The provision of such a controller having a plurality of modes of
operation, which controller guides the user in properly setting up
the dryer for the particular mode selected and prevents operation
of the dryer which is inconsistent with the mode selected.
The provision of such a controller which keeps track of a
multiplicity of shutdown events such that a service person or the
operator may review a number of the most recent shutdowns of the
dryer so that the cause of such shutdowns may be more readily
determined and such that the service history of the dryer is better
known;
The provision of such a controller which monitors a number of
safety devices provided in the dryer and which displays a message
such that the operator can determine exactly which safety device
was out of limit and caused a shutdown of the dryer;
The provision of such a controller which differentiates between
non-safety related shutdowns and safety related shutdowns such that
in non-safety shutdowns, the grain in the dryer may automatically
be unloaded, thus preventing jamming of the unloading augers and
the like so as to minimize the number of times that the dryer must
be manually unloaded;
The provision of such a controller which allows the dryer to be set
in a continuous batch, automatic staged, or continuous flow mode of
operation as desired by the user;
The provision of such a controller which stores many dryer
operating parameters and data in memory such that a service
technician may readily review the recent operating history of the
dryer and thus accurately and quickly diagnose the cause of a
problem with the operation of the dryer;
The provision of such a controller which accurately records the
amount of grain discharged from the metering rolls such that the
drying rate and the throughput of the dryer may be displayed and
stored;
The provision of such a controller which detects abnormalities in
the operation of the metering rolls;
The provision of such a controller which improves the operation of
the metering rolls;
The provision of such a controller which permits the user to
initiate an emergency cooling procedure in the event that the grain
temperature exceeds acceptable limits;
The provision of such a controller which is capable of controlling
a plurality of different grain dryer models without alteration;
The provision of such a controller which includes both hardware and
software safety devices;
The provision of such a controller which simplifies the resetting
of various dryer parameters to predetermined settings;
The provision of such a controller which is less prone to
inaccurate indications of a fault condition;
The provision of such a controller which provides both negative and
positive checks on fan operation during fan startup;
The provision of such a controller which controls the dryer
normally even during the time changes are being made to the dryer's
parameters or the diagnostic history of the dryer is being
inspected;
The provision of such a controller which is adaptable to accept
signals indicating fault conditions associated with equipment
external to the dryer, and to control the dryer in response to said
signals;
The provision of such a controller which downloads and stores the
setting of various dryer parameters such that in the event of dryer
shutdown, or upon the normal startup of the dryer, the operating
conditions of the dryer may automatically be returned to these
previous parameters; and
The provision of such a controller which simplifies operation of
the dryer, which is reliable in operation, which is easy to install
and which may be readily serviced.
Briefly stated, a grain dryer of the present invention comprises a
housing (e.g., the inner and outer baskets) defining a path for
grain to be dried (e.g., the grain columns). A fan and heater
assembly is provided for supplying heated air to the path for
drying grain in the path. Metering rolls are provided for
controlling the flow of grain along the path. Sensors are disposed
in predetermined positions so as to detect a plurality of fault
conditions with the sensors generating a plurality of fault signals
in response to the detection of the fault conditions. A controller
is operatively connected to the sensors. The controller is
responsive to the fault signals to initiate a predetermined
shutdown procedure upon receipt of any one of the fault signals. A
memory is operatively connected to the controller for
electronically recording identifying information concerning
shutdown procedures initiated by the controller.
Other objects and features of this invention will be in part
apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a grain dryer having a solid state
controller of the present invention;
FIG. 2 is a perspective view of a modular stack grain dryer
comprising three of the dryers shown in FIG. 1 stacked vertically
one on the other;
FIG. 3 is an exploded perspective view of the upper portion of the
dryer shown in FIG. 1, with parts removed for clarity, illustrating
the wet grain inlet and a horizontal garner bin receiving the wet
grain and having a horizontal auger therein for distributing grain
longitudinally within the garner bin;
FIG. 3A is a perspective of a portion of FIG. 3, illustrating the
out of grain sensor;
FIG. 4 is a front view of the control panel for an electronic
controller for controlling operation of the dryer;
FIG. 5 is an enlarged view of the display panel of the
controller;
FIG. 6 is an exploded perspective view of a fan/heater
assembly;
FIG. 7 is an end view of the lower front portion of the dryer
illustrating a motor and belt drive for the bottom unloading auger
and a SCR motor and chain drive for driving the metering rolls;
FIG. 8 is an exploded perspective view of the front portion of the
dryer shown in FIG. 7 illustrating the metering rolls and the lower
auger;
FIGS. 9 and 9A show the dryer in phantom and illustrate the
location of various sensors with the dryer;
FIG. 9B illustrates the electrical connections between several of
the sensors shown on FIG. 9;
FIG. 10 is a cross-sectional view of one of the metering rolls
illustrating the flow path of the grain from the grain column,
through the metering roll, and into the grain discharge conduit for
being transported from the dryer via the unloading auger;
FIG. 10A is a view similar to FIG. 6 showing an alternative
construction of the lower portion of the grain dryer of the present
invention;
FIG. 11 is an exploded perspective view of the rear end of the
unloading auger illustrating a grain discharge box which receives
grain from the unloading auger, the grain discharge box having a
hinged lid which is monitored by a microswitch, constituting an
auger limit switch for terminating operation of the auger in the
event the discharge box becomes overloaded with grain, forcing open
the hinged lid;
FIG. 12 is a view taken along line 12--12 of FIG. 11 illustrating
the rear ends of the metering rolls and showing a sensor for each
of the metering rolls for monitoring operation of the meter
rolls;
FIG. 13 is an enlarged view of one of the metering roll sensors
with the cover removed showing a slotted wheel mounted on and
rotatable with the metering roll and an optical encoder for
generating a signal in response to rotation of its respective
metering roll;
FIG. 14 is an elevational view of the front end of the dryer shown
in FIG. 1 showing the location of a variety of sensors used to
monitor operation of the dryer;
FIG. 15 is a schematic of the power wire circuit for the two fan
dryer illustrated in FIG. 1 connected to 230 volt, single phase
power:
FIG. 16 shows the wiring connections between the power wire circuit
shown in FIG. 15 and the computer controller located within the
control panel shown in FIG. 4;
FIG. 17 is a schematic diagram of a primary safety circuit for the
dryer of FIG. 1;
FIG. 18 is a schematic diagram of a flame detection safety circuit
for the dryer of FIG. 1;
FIG. 19 is a block diagram illustrating the interface between the
various sensor inputs used with the dryer of FIG. 1 and the
computerized control circuit of the dryer;
FIGS. 19A-19E are electrical schematics of the circuitry of FIG.
19;
FIG. 20 is a block diagram illustrating control over the various
components of the dryer of the present invention by the use of
triacs and relays;
FIGS. 20A-20F are electrical schematics of the circuitry of FIG.
20;
FIG. 21 is a block diagram illustrating the computerized control
circuit of the dryer of the present invention;
FIGS. 21A and 21B are electrical schematics of the circuitry of
FIG. 21;
FIG. 22 is a perspective view with parts cut away for clarity
illustrating a batch bin grain dryer controlled by the computerized
control circuit of the present invention; and
FIG. 23 is a sketch illustrating a further improvement of the
control system of the present invention.
Corresponding reference characters indicate corresponding parts
throughout the several views of the drawings.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, a combination grain dryer is
indicated in its entirety by reference character 1. As is
conventional, dryer 1 is mounted on a frame F which in turn may be
mounted on suitable over-the-road wheels (not shown) for the ready
transport of the dryer from one site to another. The grain dryer
includes a housing H which comprises an outer basket 3 of a series
of sheet metal screen panels 5 bolted together in side-to-side
abutting relation to form the outer basket. The perforations in the
screen panels are sized to permit drying air to readily pass
therethrough, but are sufficiently small so as to confine the grain
to be dried within the screen panels. An inner basket, as indicated
at 7, is disposed within and is generally concentric with outer
basket 3. The inner basket is also composed of a series of
perforate screen panels with the interior of the inner basket
constituting a dryer chamber or plenum 9. At the top of outer
basket 3, a horizontally disposed wet grain or garner bin 11 is
provided. At one end of the horizontal wet grain bin, a grain inlet
opening 13 is disposed, into which a conveying auger (not shown in
FIG. 1) is inserted so as to deliver or supply wet grain to be
dried in dryer 1. A horizontal top auger 15 is mounted within wet
grain bin 11 on oil impregnated hanger bearings in such manner as
to be level. Top auger 15 is driven by an auger motor 17 (FIG. 3)
via a belt and sheave arrangement 17A.
As shown in FIG. 1, inner basket 7 is generally in the form of a
diamond with an apex 19 at the top thereof which serves to divide
the flow of wet grain from wet grain bin 11 into two uniform grain
columns GC (which defines a path for the grain to be dried) on
either side of the inner basket apex and confined between the inner
faces of the outer basket 3 and the outer faces on the inner
basket. The thickness of the grain column GC is substantially
uniform from top to bottom. As shown, the thickness of the grain
column is about fourteen (14) inches and the length of the grain
column is substantially the full length of the dryer and may range
between about fourteen (14) feet up to about twenty-six (26)
feet.
More specifically, the inner basket has upper inclined panels 21
diverging downwardly and outwardly from apex 19 and vertical side
walls 23 extending down from the outer ends of the inclined panels
21. The inner basket is completed by means of lower converging
panels 25 which close the lower regions of the inner basket. All of
the panels 21, 23, and 25 of the inner basket are of perforate
sheet metal with the openings in the panels sized to permit air to
flow therethrough, but are sized to confine the grain as the grain
column flows over and around the inner basket as it is dried by
heated air emitted from drying chamber 9 in the manner as will be
hereinafter described in detail.
Outer basket 3 is generally of the same diamond shape as the above
described inner basket 7 having upper inclined panels 27, vertical
side panels 29, and lower converging panels 31. This allows for
less expensive repairs and permits variations in the material used
in the various panels to put more corrosion resistant material in
the panels which tend to corrode more rapidly, thereby promoting
corrosion resistance while minimizing the attendant cost of the
dryer. The panels of both the inner and outer baskets have
upstanding flanges 33 thereon such that the flanges of one panel
abut with the flanges of an adjacent panel. The adjacent panels are
securely fastened to one another by means of bolts inserted through
the abutting flanges 33. It will be understood that these panels
(along with many of the other components herein described) are
preferably made of corrosion (rust) resistant material, such as
galvanized sheet steel material. In some applications, it may be
preferred that the perforate panels be of suitable stainless steel
for added corrosion protection.
As indicated at 35 (FIGS. 1 and 10), adjustable metering gate
panels are provided at the lower reaches of inner basket lower
panels 25 to force the grain flowing down the grain columns GC to
be discharged from the grain column by way of a grain throat 37. A
rotary driven metering roll 39 is disposed within grain throat 37
for positively discharging a known quantity of grain upon each
revolution of the metering roll. Each metering roll 39 is
preferably driven by means of a suitable variable speed dc motor
40, controlled by a silicon controlled rectifier control circuit
SCR, and a chain and sprocket drive C (as shown in FIGS. 7 and 8).
Chain and sprocket drive C includes a plurality of sprockets SPR
designed in conventional manner to drive the metering rolls at the
rate set by the motor 40. The means of attaching the sprockets to
the metering rolls and to the motor is conventional as well.
Each metering roll 39 is a star-shaped roll (as best shown in FIGS.
10 and 11) of hardened, extruded aluminum having a plurality of
teeth (e.g., six teeth) extending radially therefrom with the teeth
extending lengthwise of the metering roll. Each time the metering
roll is rotated, the space between adjacent metering roll teeth is
filled with grain when the space faces upwardly into the grain
column. As the metering roll is rotated, the grain carried within
the space between adjacent teeth of the metering roll is carried
with the metering roll and is dumped into a grain discharge conduit
41 below the metering rolls. Thus, upon each revolution of the
metering rolls, a predetermined volume of grain is metered from the
grain column and is discharged into the discharge conduit. Metering
gates 35 are adjusted relative to metering rolls 39 such that grain
does not flow past the metering rolls. As a result the only way for
grain to be discharged from the grain column GC into the discharge
conduit is for the grain to be positively metered by the metering
rolls upon rotation thereof. Thus, metering rolls 39 and the
variable speed motor 40 constitute means for controlling the flow
of grain through the grain column GC and for controlling the rate
at which grain is discharged from dryer 1 and into the discharge
conduit 41. The drive mechanism for the metering rolls preferably
includes suitable means for reversing the direction of rotation of
the metering rolls. The control circuit is programmable to reverse
the direction of rotation of the metering rolls at preset
intervals. For example, the control circuit may be programmed to
reverse the direction of rotation of the metering rolls for five
minutes during each three hours of operation. This feature prevents
fines from building up in the corresponding grain columns GC, which
would otherwise slow the flow of grain and potentially cause an
overheated condition in the grain column.
At the rear end of dryer 1, metering roll sensors, as generally
indicated at 39a, are mounted for sensing rotation of metering
rolls 39 and for generating corresponding signals in response to
rotation of the metering rolls. As shown in FIG. 12, the rear ends
of the metering rolls are enclosed within a sensor box 39b. In FIG.
13, the cover has been removed from sensor box 39b to illustrate a
slotted wheel 39c mounted for rotation with its respective metering
roll 39. An optical encoder 39d is mounted within the sensor box
which generates a pulse signal each time one of the teeth on wheel
39c breaks a light beam. The encoder then sends these signals to
the controller for purposes that will hereinafter appear. It should
be understood that although it is preferred for many applications
to include metering rolls 39 to meter the discharge of the grain,
the present invention is not so limited. For example (see FIG.
10A--sheet 6), the metering rolls may be completely removed and the
grain allowed to fall into the discharge conduit 41. In this
embodiment, the presence of grain as the dryer starts to fill is
sensed by a paddle switch 42. The paddle switch continues to sense
grain until the dryer is almost completely unloaded, at which point
it signals the unloaded condition of the dryer to the control
circuitry.
An unloading auger conveyor 43 (FIG. 11) is provided in discharge
conduit 41 for conveying or transporting the dried grain
horizontally from the rear end of conduit 41 into a grain discharge
box 44. The latter has an auger limit microswitch 44a mounted
therein for determining when a predetermined excessive amount of
grain is in the grain discharge box. Normally a user supplied
transport auger or conveyor (not shown) is used to convey away
grain from the dryer to a grain storage bin or the like (not
shown). Whenever a problem occurs in this take-away system, the
grain backs up in grain discharge box 44, which pushes open the lid
of the box. When the lid opens, this opens the contacts of
microswitch 44a. The control circuit is responsive to this signal
to shut down the dryer. Microswitch 44a may be a model ZCK-L1
switch from Bodine. Thus, the unloading auger 43 constitutes means
for transporting or conveying the dried grain from the dryer. As
shown best in FIG. 7, the unloading auger 43 is driven by a motor
43a via a belt and pulley drive 43b.
Turning back to FIG. 1, at the lower reaches of outer basket panels
31, clean out doors 45 are provided which may be opened to allow
access to metering rolls 39 and to unloading auger 43. It will be
understood that the end of the discharge conduit through which the
dried grain is discharged (i.e., the left-hand end, as shown in
FIG. 1) constitutes a grain discharge outlet 47.
As generally indicated at 49, grain dryer 1 is provided with at
least one fan/heater assembly. In the dryer illustrated in FIG. 1,
two such fan/heater units 49 are provided stacked one on top of the
other. It is preferred that when more than one fan assembly is
used, that the larger fan assembly be mounted above the smaller fan
assemblies. Other similar grain dryers may have but a single
fan/heater 49 or it may have three (3) fan/heater assemblies.
As shown in FIG. 6, each of these fan/heater units comprises a
housing 51 having an intake end in communication with the
atmosphere and a discharge end in communication with drying chamber
9 within inner basket 7. Although the housing is shown as
cylindrical, other shapes such as rectangular or square could be
used as well. Each housing has a temperature limit sensor 52
disposed thereon, suitably connected to the control circuit by an
electrical connection not shown. When the temperature of the
housing exceeds a predetermined limit, the sensor 52 provides a
signal to the control circuit, which in response shuts down the
dryer. For example, a Model 2E364 sensor from W. W. Grainger may be
used as sensor 52.
A fan 53 is mounted within housing 51 proximate the intake end
thereof. Fan 53 is preferably an axial flow fan driven by an
electric fan motor 55 also located within the fan housing.
Alternatively, other fan types such as centrifugal fans may be used
instead. At the opposite end of the housing from the fan is
disposed an air switch sensor 56 for sensing whether air is flowing
from the fan. Such sensors may be either velocity or pressure
sensors, as desired.
A burner 57 is mounted within housing 51 downstream from fan motor
55. This burner burns a suitable fuel, such as vaporized liquid
propane, fuel oil, or natural gas, so as to form a flame within
housing 51 for heating the airstream flowing through the housing.
Of course, other forms of heater units (such as electric heaters)
could be used instead, depending upon the requirements. As shown in
FIG. 6, the flow of vaporized propane to burner 57 is controlled by
a solenoid valve S which in turn is controlled by the control
system for the dryer in a manner described hereinafter. A sensor
57A is also disposed along the propane line to sense when the
temperature of the vapor exceeds a predetermined limit. This sensor
is also connected by a suitable electrical connection (not shown)
to the control circuit. When a high vapor temperature condition
occurs, the control circuit in response to the signal from sensor
57A shuts down the dryer. Sensor 57A may be, for example, a Model
3000-563-TBD sensor from Elmwood Sensors.
The heating capacity of these burners may range from about 3.5
Million BTU/Hr. to about 10.25 Million BTU/Hr., depending on the
size of the dryer and the burner. The flame mixes with the
airstream flowing through housing 51 and thus heats the air flowing
through housing 51.
The heated air and the products of combustion (primarily carbon
dioxide and water vapor) are mixed with the airstream downstream
from housing 51 in an air mixing chamber 59 (see also FIG. 1)
having air mixing vanes 61 therein. The mixing chamber 59 receives
the airstream from the discharge end of housing 51 and the vanes 61
thoroughly mix the air and the products of combustion before this
mixture is released into drying chamber 9. Although the mixing is
shown as circular in FIG. 1, it should be understood that the
mixing is actually quite turbulent. The fan and the burner
above-described are conventional.
Drying chamber or plenum 9 has dividers 63 (FIG. 1) therein which
divide the drying chamber into different heating zones. The
fan/heater units 49 may thus be controlled so as to provide heated
air of a desired temperature and flow rate to the various zones
within the drying chamber such that the air discharged from the
drying chamber, through the perforated panels comprising the inner
basket and into the grain column GC, dry and condition the grain in
a desired manner as will be hereinafter described.
As shown in FIG. 2, two or even three of the dryers 1 may be
vertically stacked one on the other to form a modular stack grain
dryer MSD in which grain to be dried is loaded into the wet grain
bin 11 of the top dryer and then the various fan/heater assemblies
49 of the stacked dryer are controlled to dry the grain in
accordance with predetermined heating zones as the grain travels
downwardly in the grain columns GC of the various dryers. It will
be understood that in a modular stack dryer that only the bottom
dryer 1 need be provided with metering rolls 39. The drying
capacity of grain dryers as herein described may vary between about
120 bushels of shelled corn/hour for a single stage, low capacity
single fan dryer (such as a Model 1108 dryer commercially available
from Grain Systems, Inc. of Assumption, Ill., the assignee of the
present invention) and about 4,100 bushels/hour for a high capacity
modular stack dryer MSD having three (3) vertical dryer modules and
six (6) fans (such as a Model 3626 illustrated in FIG. 2 also
commercially available from Grain Systems, Inc.).
A weatherproof electrical panel box 65 (FIG. 1) contains circuit
breakers and switches for supplying electrical power to the various
motors powering the augers, metering rolls and fan/heater units of
grain dryer 1. This panel is adapted to be connected to power lines
via a service line (not shown). It will be understood that,
depending on the electrical service available at the site where the
dryer will be operated, the electrical power may be 230 volt single
phase, 230 volt three phase, or 440 volt three phase power. At many
farms where dryer 1 will be used, the available power is 230 volt
single phase power. It will be noted that the current draw for such
dryers may vary considerably. For example, for the Model 1108 dryer
described above, it has a steady state current draw of about 62
amps if connected to 230 volt single phase power or about 36 amps
if connected to 230 volt three phase power. The larger Model 3626
dryer has a steady state current draw of about 352 amps if serviced
by 230 volt three phase power or 176 amps if serviced by 440 volt
three phase power. It should be understood that the voltages needed
by the various motors and control circuitry may differ from the
supply voltage, in which event those voltages may be stepped down
to the desired voltage level by conventional means.
It will be understood that if the various electric motors of dryer
1 are started simultaneously, the startup current draw for these
motors could be considerably higher and may exceed the capability
of the power service. It will be further understood, that a
manufacturer of grain dryers, such as above described, must furnish
a wide range of models to meet the needs of small grain farmers for
on-farm drying to large commercial grain dealers who must dry large
quantities of grain in short times as the wet grain is delivered
from the field. For example, Grain Systems, Inc. offers
approximately sixty-two (62) different models of grain dryers.
The solid state electronic control circuitry of the present
invention is provided within a weatherproof cabinet 69 (FIG. 1)
having a transparent panel 71 through which the user/operator of
dryer 1 may monitor various dryer operating parameters without
having to open the cabinet. The circuitry, described below,
includes (see FIGS. 4 and 5) a control panel 73 which has various
manually operable input devices (described below) and an
alpha-numeric display 75 mounted within cabinet 69. The control
panel and the display panel will be described hereinafter. Both the
control panel 73 and the electrical panel box 65 are mounted on the
front of dryer 1 for ready access by the operator. Suitable
electrical connections are made between panel box 65 and cabinet
69, as described below.
Turning to FIG. 3, it can be seen that garner bin 11 has sides 11A,
a floor 11B, ends 11C, and a top 11D, which define the conduit
through the bin. Auger 15 is driven by motor 17, through belt and
pulley drive 17A, to transport grain from bin opening 13 along the
conduit to cause the grain to fall into grain columns GC. It should
be appreciated that auger 15 operates to fill the garner bin
conduit with grain until the conduit is full. At that point it
ceases operation until the grain level falls a predetermined
amount. More particularly, the control circuitry is responsive to
signals from a sensor housing 81 to control motor 17 to function in
this way. Housing 81 is electrically connected by an electrical
cable 83 to the control circuitry (described below). The housing is
mechanically attached to a switch shaft 85 which in use is disposed
across the end of the garner bin conduit. The shaft carries a
downwardly extending grain paddle 86 which is in contact with the
grain in the garner bin. As the level of grain in the conduit
increases, the paddle 86 is moved upwardly by the grain and rotates
shaft 85 in one direction, and as the level of the grain in the
garner bin decreases, the switch shaft moves in the other
direction. The shaft is rigidly mounted to the housing so that
movement of the shaft causes corresponding movement of the housing.
As shown in FIG. 3A, housing 81 has a mercury switch 87 fixedly
mounted thereto, so that movement of the housing to a predetermined
position causes switch 87 to send a signal to the control circuitry
that the grain has reached corresponding predetermined level. In
particular, mercury switch 87 is the out of grain sensor, which
signals to the control circuitry that the garner bin needs
grain.
Turning to FIG. 4, control panel 73 includes a moisture control
portion 91, a control switch/potentiometer section 93, and a
display/membrane switch section 95. Moisture control portion 91
includes a moisture control thermostat 91A and an on/off switch
91B. The moisture control thermostat preferably controls the
discharge grain moisture from the dryer by sensing grain column
temperature, using grain column temperature sensors described
below. By adjusting the setting on thermostat 91A, the user may
adjust the desired moisture level of the dried grain exiting from
the dryer. The control circuit is responsive to the setting on the
thermostat and to the grain column temperature to control the
metering rolls 39 to prevent the grain from exiting the dryer until
the desired moisture level is reached. The way in which this is
done depends upon the mode of operation of the dryer.
The grain dryer has a number of modes of operation, and a number of
user selectable speeds of operation. For example, a user operable
switch 97 is used to select the drying mode of the dryer. The
possible selections are "Staged Batch" and "Continuous Flow." The
control circuit is responsive to this switch setting to control the
dryer to operate in the selected mode. In a similar manner, an
unload switch 99 is used to signal the control circuit whether "1
Speed" or "2 Speed" operation of the metering rolls 39 is desired.
When the drying mode switch 97 is set for "Continuous Flow" and the
unload switch is set for "2 Speed" operation, the control circuit
is responsive to the moisture control thermostat setting and to the
grain column temperature to switch the metering rolls 39 between
the low and high speeds as a function of discharge moisture. If the
grain moisture (as indicated by the grain column temperature) is
increasing above a level corresponding to the desired moisture
level, the low speed of metering rolls is used. As the moisture
level decreases, the metering rolls are switched to the high speed
of operation. In this situation, the discharge auger 43 is
controlled by the control circuit to operate continuously.
The user can select the actual high and low speeds of the metering
rolls 39 by using a pair of potentiometers 101, 103. The control
circuit is responsive to the user entered setting on the
potentiometers to control the metering rolls to operate at the
corresponding speeds. More particularly, the low speed setting on
potentiometer 101 determines the low speed of metering rolls 39
only when the two speed automatic moisture control feature of the
dryer is utilized. The high speed setting is used in four
situations. The first is during the two speed automatic moisture
control mode of operation, described above. The second is when the
unload switch is set in the "1 Speed" position, that one speed of
operation being the speed set by high speed potentiometer 103. In
this situation, the control circuit is responsive to the moisture
control thermostat setting and the grain column temperature to
switch the metering rolls either on to the setting of the high
speed potentiometer 103, or off, depending on the grain moisture.
The third is when the dryer is operating in continuous mode and the
moisture control is not used. The fourth is when the grain is being
discharged from the dryer during the unload cycle of staged batch
dryer operation. In this mode of operation, the control circuit is
responsive to the moisture control thermostat 91A setting to hold
the grain in the dryer until the desired moisture content is
reached. When the grain is dried to the desired setting, the
control circuit controls the metering rolls to unload the dryer at
the high speed set on potentiometer 103.
The switch/potentiometer section 93 also include a manually
operable switch 105 for selecting the mode of operation of load
auger 15. This switch has an "Off" position, and two mode
positions, "Auto" and "Manual." The control circuit is response to
switch 105 being in either the "Auto" and "Manual" positions to
operate load auger 15 whenever the dryer is low on grain and to
automatically shut off the load auger when the dryer is full. The
control circuit determines these conditions from mercury switch 87
in the garner bin, described above. When the switch is in the
"Auto" position, the control circuit also shuts the entire dryer
down if the flow of grain to the dryer is interrupted. This
condition is evidenced by mercury switch 87 providing the "needs
grain" signal for a preset period of time. That preset period of
time is selectable by the user, using a set of membrane switches
described below in connection with FIG. 5. Note, as described
below, that the first time the mercury switch senses the need for
grain at startup of the dryer there is no delay. It is only after
the garner bin has been filled the first time that the time delay
is used to prevent too rapid recycling of the load auger. If user
provided auxiliary equipment is being used with dryer 1, load auger
switch 105 can also be used to control operation of the auxiliary
equipment in the same manner.
Each fan 53 has a corresponding fan switch 107 disposed on panel
73. Each switch has an "Auto" position, an "Off" position, and an
"On" position. In FIG. 4, two such switches are shown, the upper
one for the upper fan and the lower one for the lower fan in FIG.
1. When the switches are in the "On" position, the control circuit
controls the fans to operate continuously. The control circuit is
responsive to the switches being in the "Auto" position to operate
the fans continuously except when the dryer is in the unload cycle
of staged batch dryer operation.
Similarly, each heater 57 has a corresponding heater switch 109,
having an "Auto" position, an "Off" position, and an "On" position.
The control circuit is responsive to each heater switch being in
the "On" position to cause the corresponding heater to operate
whenever its associated fan is operating. In the "Auto" position,
the control circuit causes the burner to operate only during the
dry cycle of staged batch operation.
It should be noted, as discussed below, that the control circuit of
the present invention controls all aspects of the fan and heater
operation. Starting, operation, and monitoring of the fans and
heaters are all under direct control of the control circuit, as
will appear. Operation is controlled automatically in accordance
with the program preset for that particular model of dryer in the
control circuit. Even the response of the fans and heaters during
the various shutdown procedures is preset, so that even the
shutdown procedures are automatic, requiring no operator
intervention.
Panel 73 also includes a "Control Power" switch 111, and "Outside
Light" switch 113, a "Start" switch 115, and a "Stop" switch 117.
The control power switch 111 is used to turn power on and off to
the control circuitry. The outside light switch is used to turn on
and off an external illumination device 118 (FIG. 14) mounted for
the user's convenience on the dryer. The light switch also has an
"Auto" position in which the light in on whenever the dryer is
operating. The control circuit turns off the light upon shutdown of
the dryer. It therefore functions as a remote indicator of dryer
operation. The start switch 115 is used to energize the control
circuitry. When this switch is depressed, the dryer starts up and
operates based on the other control panel switch settings. If the
other switches are in the "Off" positions, the individual dryer
components may be operated by first depressing the start switch and
then turning on the switch for the individual dryer component.
The stop switch is used to stop all dryer functions. In the event
of an automatic dryer shutdown (described below), stop switch 117
must be pressed to reset the dryer control circuit before the dryer
can be restarted.
Also shown in FIG. 4 is the display/membrane switch portion 95,
shown in more detail in FIG. 5. This portion of the control panel
includes a three line, multi-character liquid crystal (LCD) display
119 for displaying messages and other information, three LCD
displays 121, 123, 125 for displaying timer information, a set of
timer membrane switches 127, a set of delay membrane switches 129,
a set of program membrane switches 131, a total bushels membrane
switch 133, and a reset membrane switch 135. It is preferred that
LCD displays 119, 121, 123, and 125 be part of a single four line,
twenty character per line display, suitably masked off as
indicated. To energize the switches of portion 95, the user turns
control power switch 111 (FIG. 4) to the "On" position. When this
occurs, the control circuit causes the total running hours of the
dryer and the current time and date and model of the dryer to be
displayed in display 119. Display of the model of the dryer allows
verification that the correct control software for the control
circuit is enabled. The control circuit itself is activated by the
user pressing reset membrane switch 135.
The control circuit of the present invention has five built in
timers, labeled "Dry", "Cool", "Unload", "Out of Grain", and "Aux
1." These timers have associated therewith membrane switches 137,
139, 141, 143, and 145, which the user may operate to set the
associated timers. The control circuit is responsive to these
switches to set the corresponding timers in the conventional
manner. The Dry, Cool, and Unload timers are used to set the cycle
times in the "Staged Batch" mode only. To use and display the
settings on these three timers (in displays 121, 123, and 125
respectively), the "Drying Mode" selector switch 97 must be in the
"Staged Batch" position. If it is, the control circuit causes the
current settings on these three timers to be displayed in the
display (121, 123, 125) disposed above the corresponding timer
membrane switch.
To change the setting of these timers, the user must press the
desired Dry, Cool or Unload timer membrane switch, press a program
membrane switch 147 labeled "Modify", and then press either a
program membrane switch 149 labeled "Increase" or a program
membrane switch 151 labeled "Decrease" until the desired setting
appears in the corresponding display (121, 123, 125). The control
circuit is responsive to the increase and decrease switches to
change the display of the setting accordingly until the actuated
switch is released. Once the desired setting is displayed, the user
presses a program membrane switch 153 labeled "Enter." The control
circuit in response changes the setting of the corresponding timer
to that displayed in the corresponding display.
The user is not required to remember this procedure for changing
timer settings. Once the desired timer membrane switch is pressed,
the control circuit causes messages to be displayed on display 119
to guide the user through the procedure.
Displays 121, 123, and 125 also have another function. During dryer
operation, the time remaining on each timer is displayed on the
corresponding display. Should power be lost to the dryer or should
the dryer be stopped, the control circuit keeps those times in
memory. Upon restart of the dryer, the timers continue timing down
from those stored times. The user can set each timer to its initial
setting by pressing the reset switch 135. The control circuit in
response resets all timers to their initial values.
The out of grain timer, associated with membrane switch 143, causes
the control circuit to automatically shut off dryer 1 after the
period of time set on that timer should the dryer run low on grain.
Before this feature is enabled, the load auger switch 105 must be
in the "Auto" position. The procedure to change the setting of this
timer is the same as that described above in connection with the
Dry, Cool, and Unload timers.
In addition to the timers, the control system of the present
invention has four delays, associated with four delay membrane
switches 155, 157, 159, and 161, labeled "Load", "Unload", "Aux 1",
and "Aux 2" respectively. The load delay is used to delay the
starting of the load auger when the dryer fill switch 87 is
activated to prevent the load auger from cycling too quickly. Note
that the load delay is not used when the garner bin is being filled
the first time after the Start or Auto switches are actuated. This
allows the dryer to be filled without delay upon startup, while
still preventing the load auger from cycling too quickly
thereafter. The unload delay is used to delay the stopping of
unload auger 43 after the metering rolls 39 stop to allow the
unload auger to empty out the grain. The Aux 1 and Aux 2 delays are
available for use with user-supplied auxiliary equipment. These
delays may be set by the user in the same manner as the timers are
set, as described above.
When the dryer is operating, the control circuit causes the first
line of LCD display 119 to display the dryer mode of operation. The
second line is caused to display the bushels per hour output of
dryer 1 or the metering roll 39 rpm. The third line is caused to
display the total bushels dried. By pressing switch 133, labeled
"BPH-RPM-TOTAL BU", the user signals the control circuit to toggle
the display on the second line between showing the metering rolls'
rpm and the bushels or grain per hour that the metering rolls are
then removing from dryer 1. With respect to the third line of the
display, the total bushels figure the control circuit causes to be
displayed is the total cumulative bushels dried since the bushel
counter was last reset. This allows the user to measure the number
of bushels in a load, from a field, etc. The total bushel counter
may be reset by holding the reset switch 135 closed for a
predetermined time such as five seconds. This action also may be
used to reset a total number of batches counter (this counter is
incremented by the control circuit by one each time the housing is
unloaded when the dryer is operated in the staged batch mode) if
the dryer is running in the Staged Batch mode, and also to reset
the clock and date. In response to the signal from the reset
switch, the control circuit displays instructions on LCD display 19
for directing the user through these operations.
Turning to FIGS. 9 and 9A, the placement of various sensors used
with the control circuit are shown. Specifically, each zone of the
plenum has associated therewith a plenum high limit thermostat
sensor 171 for each zone of the plenum. These thermostat sensors
are operatively exposed to the temperature throughout the plenum by
corresponding capillary tubes 173 which operate in conventional
manner. When one of the plenum high limit sensors 171 reaches a
predetermined limit, it sends a signal to the control circuit via
suitable electrical connections (not shown) to shut down the dryer.
Sensors 171 may preferably be model T675F1008 sensors from
Honeywell.
Also shown in FIGS. 9 and 9A are a fixed limit grain temperature
thermostat sensor 175 and an adjustable limit grain temperature
thermostat sensor 177. The fixed grain limit sensor may preferably
be a model 220985 sensor from Thermo-Disc, while the adjustable
grain limit sensor may preferably be a model T675F1016 sensor from
Honeywell. These sensors are connected to capillary tubes 179 which
expose the sensors to the grain temperature substantially
throughout the length of dryer 1. The fixed grain high limit sensor
is disposed to respond to the temperature of the grain in the grain
column GC on one side of the dryer, while the adjustable grain high
limit sensor is disposed to respond to the temperature of the grain
in the grain column GC on the other side of the dryer. Signals from
sensors 175 and 177 are supplied through suitable electrical
connections (not shown) to the control circuitry. When the
temperature in the corresponding grain column exceeds the
predetermined limits set by the fixed and adjustable grain limit
thermostat sensors, the appropriate sensor sends a signal to the
control circuit indicating a high grain temperature condition. The
control circuitry in response shuts down the dryer, as described
below.
The temperature of the grain is also sensed directly by a set of
four temperature sensors 181, two of said sensors being disposed in
each grain column. It is preferred that sensors 181 be model
C7170A1002 sensors from Honeywell or the like. For convenience,
temperature sensors 181 are disposed along the capillary tubes 179,
although this is not required. Although the exact placement of the
sensors 181 is not critical, by way of example, one sensor in each
column may be placed about three feet from the front of the dryer
1, while the other sensor in that column may be placed about three
feet from the back of the dryer. The electrical connection of these
sensors is illustrated in FIG. 9B. The two sensors 181 in each
grain column are connected in series, and the two sets of sensors
are then connected in parallel to the inputs of moisture control
thermostat 91A, discussed above in connection with FIG. 4. By
connecting the four sensors in this manner, the resistance (and
hence the signal) seen by the moisture control thermostat is
comparable to that seen from a single sensor. The input to the
moisture control thermostat as a result is an average temperature
reading for all the grain in the horizontal plane through the dryer
defined by the four sensors.
A burner controlling thermostat 185 for each burner is exposed by
means of a capillary tube 187 to the temperature in the
corresponding portion of the plenum. When the temperature sensed by
one of these thermostats exceeds a predetermined value, the
thermostat activates a solenoid SB (FIG. 14--sheet 5) to change the
flow rate of gas to the corresponding burner to lower the burner
temperature. Thermostats 185, therefore, operate independently of
the control circuit to keep the burners operating within a desired
temperature range.
Also shown in FIG. 14 is an electronic safety shut-off valve 189
under control of the control circuit to shut off the gas flow to
the dryer in the event of a dryer shutdown. Valve 189 also includes
a manually operable actuator handle 191 as well. The electronic
shut off valves manufactured by Maxon have been found to work well
in this application.
Turning to FIG. 15 (sheet 6), the power circuitry for grain dryer 1
includes a safety disconnect 193 connected by suitable electric
lines, such as the lines L1 and L2 shown, to the power source,
shown as a 220 V, single phase source. Power from the safety
disconnect is supplied to a set of four circuit breakers 195
connected through appropriate contactors 197 to the unload motor
43a, load motor 17, upper fan motor 55 and lower fan motor 55.
Power from one of the circuit breakers 195 is also supplied through
a set of contactors 199 and a conventional SCR DC drive circuit 201
to metering roll motor 40. It should be understood that the number
of circuit breakers may vary according to the number of fans used
in the dryer. The speed of the motor is controlled by
potentiometers 101, 103 as described above. The connections to the
potentiometers are made through a set of three lines P1, P2, and P3
as shown.
Power is also supplied to a step-down transformer T1. The stepped
down voltage is supplied to the safety circuits and control circuit
of the present invention, as shown.
Suitable fuses F1 and overload devices OL are disposed in the
circuit as shown. In addition, a pair of relays MR1 and MR2 are
connected across the various circuit breakers to shut off power if
a fault occurs.
FIG. 16 shows the connections from the various sensors mentioned
above to the control box 69, as well as power connections to
various components. Although various sensors have been discussed
above as connected to the control circuit, it should be appreciated
that various other sensors such as the 20 second shutdowns and
customer supplied safety shown in FIG. 16 may be used as well.
The safety circuits, labeled 205 and 207, of the present invention
are shown in FIGS. 17 and 18. As shown, in safety circuit 205 the
various sensors discussed above are connected in series with twelve
volts supplied to one side of the circuit, and the other side being
connected through a connection J5-10 to a 2.5 second hardware timer
209 (as well as the shift register inputs). In safety circuit 207,
twenty second shutdown sensors 211 are connected in series with
twelve volts supplied to one side of the circuit, the other side
being connected through a connection J5-6 to a thirty second timer
213 (as well as the shift register inputs). In both cases,
connection to the control panel is made between each adjacent set
of switches, which enables the control circuit to determine not
only that a fault has occurred, but also to identify the particular
fault.
Turning to FIG. 19, most of the sensor outputs appear on pins
labeled from J1-1 to J5-10. See FIG. 16 for the pin assignments for
the more prominent sensor outputs. As shown in FIG. 19, those
outputs on pins J1-1 to J5-5, and J5-7 to J5-9, are supplied
through an input interface circuit 215 to a shift register circuit
217. In similar fashion, the output on pin J5-6 (potentially
signaling a flame detector shutdown fault--see FIG. 18) is supplied
through forty second hardware timer 213 to the shift register
circuitry, and the output of pin J5-10 (potentially signally a
safety circuit fault--see FIG. 17) is supplied through five second
timer 209 to the shift register circuitry 217. It should be
understood that the particular time constants of the hardware
timers are arbitrary and can be varied within reason as desired.
The hardware timers are shown in detail in FIGS. 19A and 19B. As
shown therein, each timer includes a 4.7K resistor (R91G, R91E)
connected between the input and ground. A 10K resistor (R96, R98)
is connected in series between the input and an inverter (U14A,
U37E). Connected between the input of each inverter and ground is a
parallel circuit consisting of a 470K resistor (R224, R229) and a
0.1 .mu.-F capacitor (C87, C85). The output of each inverter is
supplied through a diode (D1, D24) and a 1K resistor (R99, R227) in
series to the input of a second inverter (U14B, U37F). The forty
second timer also has a parallel circuit consisting of a 100K
resistor R228 and a 330 .mu.-F capacitor C169 between the input of
the second inverter and a five-volt source. The output of the
second inverter in each case is supplied to the shift register
circuitry 217. In the case of the five second timer, that output
also is supplied to the circuitry (described below) as a hardware
safety shutdown signal-1, which will shut down the dryer operation
even if the software safety measures, described below, fail.
Similarly, in the case of the forty-second timer the output of the
second inverter is supplied through a diode D25 to provide a second
safety shutdown signal, labeled signal-2.
The shift register circuitry 217 receives a clock signal and a
strobe signal from a computer 219, which forms the core of the
control circuitry of the present invention. More specifically,
computer 219 supplies the dock and strobe signals to the shift
registers through suitable interface circuits 221, 223. In
response, the shift registers, as described below send serial data
back through a suitable interface 225 to computer 219. Shift
register circuitry 217 preferably includes a number of cascaded
shift registers. For example, eleven cascaded 4021-type parallel
in/serial out shift registers have been found to be satisfactory
for this purpose.
Computer 219 operates under programmed control, and is preferably a
microcontroller of the MCS-51 family of Intel microcontrollers,
such as a TP83C51FA microcontroller. Any programming language may
be used to program the controller. Of course the control system of
the present invention could be implemented instead using other
types of microcontrollers, microprocessors, or even more
traditional computer systems such as personal computers or
minicomputers as the process controller.
The software which control computer 219 and the electronic
circuitry described herein control all aspects of the operation of
grain dryer 1, including grain handling, safety input monitoring,
heater control, operational statistics tracking, error logging, and
failure diagnostics. These key features operate as described below.
The software executes in real time in the sense that the control
circuit is able to detect and respond to events in a short enough
period of time that the system can adequately control the process
being monitored. As will become apparent, computer 219 relies on
interrupts from external sources and an internal clock to schedule
and control dryer operations. Tasks managed by the software fall
into two general categories--foreground tasks and background
tasks.
The foreground tasks are those easily visualized activities such as
turning motors off and on, reading control switch inputs, updating
the LCD display, etc. These activities occur frequently, in many
cases several times each second, but do not have to happen at any
precise time. The background tasks in contrast are the somewhat
invisible activities of the system. These tasks include counting
pulses from the metering roll sensors 39d whenever they arrive;
generating signals to keep hardware watchdog timers from shutting
down the system; running the software timers that control
sequencing of motors, error detection, etc.; and scheduling
"slower" activities like calculating RPM or updating the LCD screen
that need only occur once each second. In the dryer 1 control
system some of these background activities occur as frequently as
once every 120 microseconds.
The electronic controls used in the present system are particularly
suited for grain dryer 1. All input signals except the metering
roll pulse inputs from sensors 39d are essentially the same whether
the input source is a control switch or a set of contacts on a
safety sensor. There are two types of output circuits--triac
outlets and relay outputs. See the discussion below with respect to
FIGS. 20-20F for a discussion of the output circuits.
Turning to FIGS. 19C-19D, the first stage, labeled U11, of cascaded
shift register circuit 217 is shown. It has eight inputs, an output
line for supplied data to computer 219, a strobe input, a clock
input, and an input for receiving data from the next stage. Each
sensor output (see FIG. 19D) is supplied through a filter
consisting of a 4.7K resistor R91, a 47K resistor R94, and a 0.1
.mu.-F capacitor C81 connected as shown to a corresponding pin of
its associated shift register. The input interface circuitry 215,
therefore, consists of such resistor/capacitor circuits for each
sensor output. Each input to a shift register is fed to the
corresponding one of eight input lines of its associated parallel
to serial shift register, such as register U11. The 4.7K resistor
R91 is connected between the input terminal and ground, so that it
also serves as a "pull down" to keep the shift register input near
zero volts unless the 12 volt safety signal has kept it high. This
is another safety feature of the overall dryer design. If anything
goes wrong, even a safety circuit wire breaking, the dryer controls
will detect an error condition and shut down the system.
When a fresh set of input readings is required by the system the
microcontroller 219 sends out a strobe pulse that latches the
current state, high or low, of each input pin into the shift
register. This puts a "snapshot" of all inputs into the registers.
Once the current states have been latched into the shift registers
the microcontroller shifts this data into its internal memory one
bit at a time by clocking the registers. A total of 112 bits of
data are read and stored when this occurs. This data is shifted
into the microcontroller a total of three times. These three sets
of data are compared to one another and must be identical before
the computer takes action. If all three readings are not the same,
a fresh reading of the inputs is strobed into the latches before
the program continues. This prevents the computer from using any
bogus data that may have been garbled by electrical noise. The data
is supplied from the shift registers in serial form, so that all
the data passes through first stage register U11. That chip
supplies the data one bit at a time through interface circuitry
225. That circuitry includes a 4.7K resistor R107 connected to the
base of a transistor Q1. The collector of the transistor supplies
the data through a resistor capacitor network consisting of a
100-ohm resistor R108, a 4.7K resistor R39, a 10K resistor R22 and
a 100 pF capacitor C43, to the input of an inverter U7C. The output
of inverter U7C is supplied to a serial data input interface 231,
which in turn supplies the data to computer 219. Serial data input
interface 231 is described in detail below in connection with FIG.
21A.
The interface circuitry 221, 223 which computer 219 uses to supply
the strobe signals and clock signals to the shift registers (and to
the rest of the control circuitry) is shown in FIG. 19E. The
circuits for each are essentially identical. The signal from the
computer is provided to a transistor (Q3, Q4) whose output is fed
through a resistor/capacitor network consisting of a 100 ohm
resistor (R30, R31), a 2.2K resistor (R216, R219), a 10K resistor
(R217, R218), and a 100 pF capacitor (C153, C154) to the input of
an inverter (U14F, U37C). The output of inverter U14F is the clock
signal, and the output of inverter U37C is the strobe signal.
Outputs work in a similar fashion to the digital inputs. See FIGS.
20-20F. Computer 219 has stored in internal memory a pattern of
bits that corresponds to the on/off conditions of the system triacs
and relays which are used to turn off and on the various motors and
other devices discussed above. This information is supplied to a
set of triac and relay drivers 233 two times. The triac/relay
drivers comprise a set of cascaded serial to parallel output
registers, such as the drive latch U18 shown (FIG. 20A). It has
been found that a cascaded set of three UCN5895-type serial to
parallel output registers work satisfactorily in the present
invention. The first data that is sent out is simultaneously
shifted back into the microcontroller. If it receives back what it
sent out, a signal is sent to the output registers that latches the
data to the outputs of the integrated circuits which turn on triacs
and relays.
More specifically, computer 219 sends data in serial fashion to
shift register U18 (and through that register to the other
registers making up triac and relay driver circuitry 233) through
an interface circuit 237. Interface circuit 237, as shown in more
detail in FIG. 20E, includes a transistor Q5 which is connected to
the computer to receive data. A 10K pull-up resistor R3 is also
connected to that particular pin of the computer. The output of the
transistor is supplied through a resistor/capacitor network
consisting of a 100 ohm resistor R32, a 2.2K resistor R220, a 10K
resistor R221, and a 100 pF capacitor C155 to the input of an
inverter U37D. The output of inverter U37D is connected to the
"Data In" pin of the shift register U18. As mentioned above, this
data is also simultaneously shifted back to microcontroller 219.
This is accomplished using interface circuit 239, shown in more
detail in FIG. 20F. Interface circuitry 239 takes the serial data
from the data out pin of chip U18 and supplies it through a 4.7K
resistor R209 to the base of a transistor Q20. The collector of
transistor Q20 is connected through a resistor/capacitor network
consisting of a 100 ohm resistor R208, a 4.7K resistor R41, a 10K
resistor R40, and a 100 pF capacitor C44, to the input of an
inverter U7E. The output of inverter U7E is supplied to computer
219. A 10K pull-up resistor R3 is also connected to that pin of
computer 219.
The clock and strobe signals are supplied to chip U18 from the
computer using the interface circuitry 221 and 223 described above
in connection with FIG. 19E.
If the data received back from the drive latch/shift registers is
the same as what was sent out, computer 219 uses interface circuit
241 (shown in detail in FIG. 20D) to signal the shift registers to
load or latch the data to the outputs of the drive latches (such as
chip U18). The load signal is supplied by the computer through a
100K resistor R18 and a diode D6 to the input of an inverter U6C.
The input of the inverter is also connected to the diode/capacitor
junction of a series circuit consisting of a 22K resistor R10, a
diode D4, and a 22 .mu.F capacitor C7. The output of inverter U6C
is provided to a transistor Q1, whose output is supplied through a
resistor/capacitor network consisting of a 100 ohm resistor R19, a
2.2K resistor R211, a 10K resistor R212, and a 100 pF capacitor
C150 to the input of a second inverter U14E. The output of the
second inverter is supplied through a diode D16 to a third inverter
U14d, whose output is directly connected to the enable pin OE-bar
of each drive latch. A 47K resistor R213 and both hardware safety
shutdown signals are also connected to the input of third inverter
U14D. As a result, the hardware safety shutdown signals can shut
down the dryer (by shutting down the triacs and relays) even if the
computer software safeties should completely fail.
The two basic types of output control devices of the present grain
dryer control system are triacs and relays. A triac, as is known,
is a solid state device that switches 120 VAC on or off based on
the state of the signal on its input. The relays used in the system
have both normally open and normally closed contacts. When
activated by its control signal the relay "pulls in", closing the
normally open contacts and opening the normally closed
contacts.
A triac control is shown in FIG. 20B, while a relay control is
shown in FIG. 20C. It should be understood that all triac controls
are identical, as are all relay controls. The triac control
includes an optocoupler U34 (such as an MOC3022-type optocoupler)
having its input connected to the corresponding output drive the
associated drive latch (such as chip U18). When the proper input
signal is present, this turns on a triac Q17 having its gate
connected to the output of the optocoupler. When triac Q17 is on it
allows power from line L1 and neutral NT to flow through the
associated load. In the case of FIG. 20B, the illustrative load is
the motor 43a for the unload auger. It should be understood that
each motor has its own triac or relay.
Operation of the relay controls (see FIG. 20C) is similar. The
corresponding output from the associated drive latch directly
energizes a relay such as relay RL5, which in conventional manner
opens the normally closed set of contacts and closes the normally
open set of contacts.
Turning to FIG. 21, computer or microcontroller 219 is connected in
conventional manner to various devices such as a pair of
74HC573-type latches U2 and U4, a 28F512 memory chip U3, a sound
driver 251, the circuitry of FIGS. 19 and 20 (described above),
serial data input interface 231, and, through a pair of identical
interface circuits 253, to the first and second metering roll
sensors 39d. Computer 219 also includes means for resetting the
circuit, indicated generally by the line labeled "Reset." More
significantly, computer 219 is connected to a memory labeled TIC
which includes its own built in battery. Memory TIC is preferably a
model DS1494LF5 device from Dallas Semiconductor. The computer
stores fault condition and diagnostic information in the TIC memory
so that a record of dryer shutdowns may be kept and referred to
even if power is lost to dryer 1.
As mentioned above, the serial data from the various sensors used
in the present system is supplied to serial data input interface
231. This interface is shown in more detail in FIG. 21A. The serial
data from the sensors is supplied through a resistor/capacitor
network consisting of a 4.7K resistor R39, a 10K resistor R22, and
a 100 pF capacitor C43 to the input of an inverter U7C. The output
of inverter U7C is supplied to the serial input pin of a 4021-type
shift register U17. Shift register U17 may be cascaded with as many
additional shift registers as are needed to accommodate the desired
inputs. A second shift register U16 is shown, but it should be
understood that more or fewer are also contemplated. The input pins
of the shift registers are connected to the switches described
above in connection with panel 73. Computer 219 uses the strobe and
clock signals described above to serially input this information,
including the data from the sensors. A 10K pull-up resistor R3 is
connected to the output of the last shift register.
The one other input source to the computer are the metering roll
pulse inputs from sensors 39d. The pulses generated by the metering
roll sensors are routed to two external interrupt pins on the
microcontroller via identical signal conditioning interface
circuits 253 that square up the pulses and convert them to voltage
levels suitable for the microcontroller 219. That circuitry is
shown in detail in FIG. 21B. It includes a filter section
consisting of a 10K resistor R57, a resistor R11, a 10K resistor
R51, a 100K resistor R54, and a 100 pF capacitor C48. A pair of
diodes D20 and D23 are also provided for squaring up the pulses.
The signal from these components is supplied to a comparator U13D
having a 330K resistor R48 in its positive feedback loop. The
output of the comparator is provided through a 27K resistor R45 to
the input of an inverter U7D, whose output is supplied to computer
219. A 10K pull-up resistor R82 is connected to the same pin of
computer 219 as the output of inverter U7D.
The system software is such that any time a negative pulse arrives
at a meter roll input, the program is interrupted briefly and a
count of the pulses for that input is incremented. Afterwards the
program returns to whatever it was doing when the interrupt
occurred. This operation is typically completed in a few
microseconds time.
Grain Handling--Overview
The control system of the present invention uses the various
switches, sensors, and other input devices described above to sense
whether or not the dryer is low on grain, whether the grain is
above or below the desired temperature and which of several modes
will be used to operate the load auger, unload auger, and metering
rolls. System outputs are used to select various temperature probes
and operate electrical contractors that start and stop the augers
and metering rolls.
For example, with respect to the load auger, computer 219 monitors
the paddle switch 87 in the top of the dryer 1 to determine if the
dryer is low on grain. If the dryer needs grain the load auger 15
is started by activating the corresponding triac. The system
continues to monitor the status of the grain and shuts off the load
auger once the dryer is full. When the paddle switch 85, 87 signals
a need for grain a "load delay" timer is started. This timer is
implemented in software and is loaded with a user programmed value.
The system ignores the state of the paddle switch 87 and will not
allow load auger 15 to be restarted until the load delay timer has
expired. This prevents the motor 17 from being constantly started
and stopped and reduces wear on the motor, bushings, belts,
bearings, and related components that are a part of the load auger
system. Once the timer has expired, the system resumes monitoring
the status of the grain and will run the load auger as required
until the next time the auger is shut off. Note, however, that such
a delay would be inappropriate upon initial startup of the dryer
since the dryer at that point is presumably empty and no reason for
delay exists. The load delay timer is, therefore, only used after
the dryer is initially filled with grain.
The second load auger related feature is the "Out of Grain" timer.
This timer, programmable by the user, is used by the system to
detect that there is no more grain available for drying. When the
out of grain timer is enabled by the user, software tracks the
length of time the load auger 15 has been running. The timer starts
running when the load auger is turned on and is stopped when either
the load auger is shut off or the metering rolls 39 are discharging
grain. If the timer expires, the dryer is shut down and the time
and date of the shutdown are saved in the dryer's integral error
history memory (See the error logging section for details.)
Grain Handling Moisture Control
The dryer's moisture control system is used to automatically dry
the grain to the percentage moisture content desired by the user.
This is accomplished by the system continuously monitoring the
temperature of the grain being dried using sensors 181 and
controlling the rate at which the grain is discharged from the
dryer by the metering rolls 39. In accomplishing this control the
system takes into account which heaters the user has selected for
operation and the size and type of the dryer being controlled.
If the dryer is operating in "Continuous Flow" and the user has
selected "One Speed Unload" with "Moisture Control" turned on then
the dryer will discharge grain at the high rate when the grain
temperature is at or above the temperature setting of the moisture
control thermostat. No grain will be discharged when the grain is
below the desired temperature.
If the dryer is operating in "Continuous Flow" and the user has
selected "Two Speed Unload" with "Moisture Control" turned on then
the dryer will discharge grain at the high rate when the grain
temperature is at or above the temperature setting and will
discharge grain at the low rate when the measured grain temperature
is below the thermostat setting.
When the dryer is operated in the "Staged Batch" mode the moisture
control behave differently than in "Continuous Flow." At the end of
the "Dry" cycle, if the grain temperature grain reaches the desired
temperature. This is indicated by a "Temperature Hold" message on
the display screen.
Current dryer models incorporate either 1 or 2 temperature probes
depending on the size of the dryer. Single stack dryers have only
on probe; multiple stack dryers have two. The probe to be used for
the grain temperature measurement is selected by the system based
on how many heaters the dryer has and which ones will be running
during the drying cycle. This is because the most accurate moisture
control will occur when the temperature of the grain is measured in
the last stage of the dryer where heat is applied. The system is
engineered so accurate moisture control will occur even when the
user has setup the fans and heaters to cool the grain in the lower
dryer stages.
If the dryer is a single stack dryer the lower temperature sensor
is selected since it is the only one that exists.
In a double stack dryer with two heaters the lower temperature
sensor will be selected if the Burner #1 control switch is selected
for "On" or "Automatic" operation; otherwise the upper sensor is
selected. In all dryers the burner closest to the bottom is
designated as #1 and there can be a number of burners in the dryer,
each having a control switch for continuous, automatic, or off
operation.
In a double stack dryer with more than two heaters the system will
select the lower temperature sensor if Burner #2 is selected for on
or automatic operation; otherwise the upper sensor will be
selected.
In a triple stack dryer equipped with three heaters, the system
will select the lower sensor if Burner #1 is on or auto; otherwise
the upper sensor will be selected. A triple stack dryer with more
than three heater will select the lower sensor if Burner #2 will
run in on or auto and will otherwise select the upper sensor.
Grain Handling Metering Rolls and Unload Auger
The metering rolls and unload auger work in conjunction with the
moisture control system to regulate the flow of grain through the
dryer. The metering roll system governs the rate at which grain
moves through the dryer and the unload auger carries the metered
grain away and delivers it to the user's storage system.
In operation, the system will start and run the unload auger
anytime the metering rolls are turning. When the metering rolls
stop, the unload auger will continue run for the length of time the
user has programmed into the "Unload Delay" except in certain
cases. For example, if the computer detects any problem other than
an out of grain condition, it causes the unload auger 43 to stop
immediately.
The rotation rate of the metering rolls is set by the user with the
two front panel mounted potentiometers 101, 103. One pot sets the
high speed rate and the other sets the low speed rate. The system
selects the appropriate speed pot as described in the moisture
control section.
The metering roll system provides information to the portions of
the system that calculate the amount of grain processed by the
dryer and generates data that the safety system uses to determine
whether or not the dryer is operating properly. This data is
generated by sensors 39d attached to the ends of the two metering
roll shafts. As each meter roll 39 turns, the slotted wheel
interrupts a beam of infrared light sixty times per revolution.
This causes a pulse train whose frequency is directly related to
the rotational speed of the metering roll to be sent to the system
computer 219. The pulse rate for each metering roll is individually
tracked by the computer and used for calculating the Meter Roll
RPM, Total Bushels Processed, and detecting problems or errors in
the meter roll drive system. See discussion below.
Heater and Fan Control--Overview
Heaters and fans are controlled by the system based on the settings
of the control switches and the operational state of the dryer.
There are specific sequences of events that occur to start a given
heater and fan. This sequencing provides safe operation of the
dryer and deeps peak electrical supply current to a minimum as the
fans and heaters start and stop.
Heater and Fan Control--Fan Operation
Each fan in the dryer has its own control switch that the user uses
to select between off, on, or automatic operation. In the off
position the fan will never operate. In the on position the fan
will be started and will run continuously anytime the dryer start
switch has been pressed and the dryer is operating in Continuous
Flow or Staged Batch operation.
In Staged Batch Operation, when set to the automatic position, the
fans will be started and stopped under computer control. The fans
start and run during the dry and cool cycles and are shut off
during the unload cycle. In Continuous Flow Operation the fans will
run with the control switch in any position except off.
There is a "Fan Delay Timer" that comes into play when the system
starts fans in a multiple-fan dryer. Beginning at the top of the
dryer, where it is preferred that the largest fans are located, the
fan delay timer is started at the same time the fan contactor is
energized. This length of time, set to a default value of five
seconds, is programmable. Until the fan delay timer expires,
computer 219 will not attempt to start another fan.
Heater and Fan Control--Heater Operation
Each heater in the dryer has its own control switch that the user
uses to select between off, on, or automatic operation. In the off
position the heater will never operate. In the on position the
heater will run continuously as long as there is an indication of
airflow through the heater and the dryer has been started and is
running continuous Flow or Staged Batch operation.
In Staged Batch Operation, the heater will start and stop under
computer control anytime the Dry cycle is in effect or the moisture
control system has extended the Dry Cycle because of low grain
temperature. In Continuous Flow operation, the heaters will start
and run if there is airflow and the control switch is in any
position other than off.
The following sequence of tests and conditions must be satisfied
before the system will attempt to run a heater. First there must be
adequate airflow through the fan housing. Airflow is sensed by
diaphragm type switch 56 which is activated when air pressure in
the plenum closes the switch contacts. Of course air velocity in
the housing could be sensed instead.
Once the system detects that the fan 53 has been started and
adequate airflow is being produced a ten second purge timer is
started. If airflow is lost during the purge the timer sequence
starts over until a continuous purge often seconds has been
accomplished. This purge evacuates any unspent fuel from the heater
housing.
At the end of the purge cycle the heater's ignition system is
energized and the solenoid operated fuel valves S are opened. Flame
detection circuit 211 in the heater control senses the presence or
absence of flame and makes this information available to the
system. Any time the heater is energized but a loss of flame is
detected, a "20 Second Burner Timer" is started by the system. This
provides a means for the safety system (described elsewhere) to
ignore brief, acceptable flameouts and false loss of flame
indications. For example, the flame detection circuit/sensor 211
may sometimes indicate a loss of flame due to the naturally
occurring turbulence in the heater housing 51. In addition, the
burners can be set to cycle on and of deliberately for specialty
crops such as popcorn. This delay prevents such cycling from
shutting down the dryer. The twenty-second timer filters and
smoothes the sensor output to prevent these false indications. This
timer is described more completely in the safety section.
Safety Systems and Error Logging--Overview
The dryer's safety and error logging system help ensure that both
the operator and the dryer itself are protected from problems that
may occur while the dryer is operating. The safety system is
implemented in two layers. The first layer, implemented in
software, continuously scans the dryer's safety inputs for
conditions that are outside those encountered in normal operation.
Examples of these conditions that are outside those encountered in
normal operation. Examples of these conditions are fan motor
overloads, grain jams at the discharge outlet, high grain
temperatures, or abnormally high temperatures in the fuel supply,
fan housing, or plenum. The software can also detect two types of
failures in the metering roll drive system.
The second layer of the safety system is implemented in hardware.
This layer serves as a backup to the computer system and operated
totally independently to ensure that even if the computer did not
detect a problem for some reason, the dryer would still be shut
down.
Safety Systems and Error Logging--Directly Sensed Errors
Most dryer error conditions are directly sensed by the system. From
the schematics discussed above, it can be seen that each sensor is
wired to its own digital input and in a series loop which
terminates at the input of one of several hardware timers on the
power 1/0 board. These hardware timers provide a second level of
error detection for the system, as described above.
Whenever any safety switch opens, a 12 V Limit signal is removed
from the input to one of the hardware timers. This causes the timer
to begin timing. When the timer times out, as described above, all
electrical power to the triacs and relays is disabled. These
hardware timers provide a second level of error detection for the
system.
As mentioned above, each digital input on the system is identical
whether it is used for a safety input or a control switch. The
input consists of a parallel to serial shift register and an input
filter circuit consisting of a capacitor and two resistors. The
filter section helps to reduce electrical noise at the input to the
shift register and provides some electrical protection to prevent
high voltages from damaging the 1/0 board if they are inadvertently
connected to the safety circuits.
The digital inputs are designed so that a failure of the input or
the safety circuit itself will shut the dryer down, not let it
operate with an undetected error. In operation each input must
sense the 12 Volt Safety Limit voltage as an indication that
nothing is wrong. If the safety signal is missing for any reason
such as an actual problem, broken wiring, or defective input
components, the system will shut down the dryer and indicate the
most probable cause of the error.
Safety Systems and Error Logging--Calculated Errors
Out of Grain conditions and metering roll failures are detected
based on calculation done by the system. Out of Grain conditions,
as described previously, are detected when the system determines
that the load auger has run for some programmed length of time
without generating an indication that the dryer is full of grain.
This time is accumulated only when the load auger is being run in
"automatic" mode and when grain is being discharged from the
dryer.
The system responds to out of grain conditions in a slightly
different manner than true errors. In most cases an error will
cause an immediate shutdown of all dryer function. When the system
detects an out of grain condition, the dryer operations are stopped
but the unload auger is allowed to run through the unload delay or
"cleanout" period before stopping.
Two types of metering roll failures can be detected. The first case
is when the system has turned on the metering rolls but no rotation
is sensed. This is accomplished by running a two minute timer any
time the metering rolls are turned on. The countdown timer is
contiguously reloaded anytime a pulse is received from either
metering roll sensor 39d. If no pulses are received for two minutes
the timer will expire and an error condition will expire and an
error condition will shut down the dryer 1. The timer is stopped
anytime the system shuts off the metering rolls 39 in the course of
normal operation.
The second type failure is detected when the number of pulses
coming from each sensor 39d are not roughly the same. Since the two
rolls 39 are mechanically coupled, the number of pulses received
from each sensor should be approximately the same. Once each second
the system compares the accumulated pulses and if they are not
within fifteen pulses (1/4 RPM) of one another, computer 219 causes
the dryer 1 to shut down.
Safety Systems and Error Logging--Error Logging Functions
A unique feature of the system is the ability to capture a
historical record of errors that have caused dryer shutdowns. This
error history is stored in the TIC and is available to users and
service technicians to assist in rapidly identifying dryer problems
even when shutdowns may have occurred when no one was present to
see what the dryer was doing at the time of the problem. The TIC is
used to store the date, time, and cause of the last twenty-five
dryer shutdowns.
Each time the system detects a problem, it writes a record to the
non-volatile memory TIC that include time and date information as
well as a unique ID code that indicates the nature of the error
that occurred. Up to twenty-five such records are retained at any
one time. When the twenty-sixth error is encountered, the oldest
error record is discarded and the newest added to the history. It
should be understood that the number twenty-five is somewhat
arbitrary, and that other numbers of errors could be stored as
desired depending upon the amount of non-volatile memory
available.
The error history may be viewed by the operator at any time. When
the history is displayed the most recent error is shown first.
Based on the error code stored in the record, the system displays
an easy to understand, plain text message along with the time and
date it occurred. The user may use the increase and decrease
switches 149, 151 on the control panel 73 to scroll forward and
backwards through history.
Miscellaneous System Features
The dryer system includes several notable features that aren't
related to any particular function. These general features are
described here.
Hour Meter
The system incorporates a software generated run time meter. This
accumulates the mount of time, in hours and minutes, that the dryer
has actually processed grain. This method differs from traditional
hour meters that accumulated time anytime the device is turned on.
This gives a much truer indication of how much the grain dryer has
been used. The user/operator may view the total hours by pressing
increase switch 149 at any time during operation (other than when
another function requiring the increase switch is being
performed).
Emergency Cooling
The safety system of the dryer shuts down all operation when a
problem is detected. If the system determines the cause of failure
to be one of the grain temperature related safeties, it will allow
the user to manually restart the fans to cool the overheated grain.
During this time the other safeties are still tested to detect
other non-heat related problems.
The system will only allow emergency cooling to occur for sixty
minutes. At the end of that time the dryer will again stop. If the
system detects that the grain has cooled before the sixty minutes
has elapsed, it will exit the cooling mode and stop the fans to
conserve electricity. For safety reasons the dryer never starts
except under direct command of the user when the start switch is
pressed.
Service Bypass Functions
The system includes features that allow service technicians to
instruct the computer to ignore no airflow indications in the fan
housings and meter roll system problems. In many cases it is not
possible to diagnose heater problems unless the airflow system is
bypassed. The metering roll errors can be bypassed since they are
not safely related and only effect the systems ability to calculate
the amount of grain processed.
Data Retention on Loss of Electrical Power
If the electrical power to the dryer is lost while the system is
operating, the user can resume dryer operation where it left off
once power is restored. This feature is possible because as a
course of normal operation, the values of all running batch times,
etc. are stored to the non-volatile memory TIC once each minute.
Any time the dryer controls are turned on, the timer values are
reloaded with the data stored in this non-volatile memory. When the
user depresses the start switch the dryer will restart and continue
timed operations from where it left off, accurate to within one
minute. The saving of the timer data is scheduled by the background
processing and executed in the foreground once each minute.
Out of Grain Timer Setup
The out of grain timer controls the amount of time the dryer will
attempt to load grain before it decides there is no more grain to
be processed. To assist the operator in setting this value the
dryer keeps track of how long it took to fill the dryer during the
previous load operation. When the user presses the switch to set or
check the timer value this length of time is displayed both in
actual minutes (to the nearest 1/10) and as a percentage of the
programmed out of grain time. This information makes it very easy
for the user to determine if he should shorten or lengthen the time
period.
Bushels Per Hour Calibration
The type of grain being dried and slight variations in the
mechanical tolerances of the dryer can cause the calculated total
bushels of grain processed to be inaccurate. The BPH Calibration
Factor can be programmed by the user to compensate for these
variations. Under software control it allows a range of .+-.99%
change in the calculated value of grain processed.
Total Bushels Counter
The total bushels counter is incremented each time enough meter
roll pulses have been accumulated to indicate that a bushel of
grain has been processed. This amount is adjusted by the
calibration factor described above and can be reset to 0 by the
user. The feature is useful for estimating the amount of grain
harvested from a particular field or the amount processed for a
given customer.
Help Prompts
Setup and operation of the computer controlled grain dryers is made
easy through the use of plain text help screens for every setup
function. Whenever the user is required to press a switch or change
some data value, a message is displayed with instructions on how to
perform the operation. Before actually making any change, the user
is always asked to confirm he wants to make the change and is given
the opportunity to abort without changing a parameter.
Other Features
Memory U3 has stored therein the programs for a variety of sizes or
models of grain dryers. This permits the same control board to be
used in a multitude of different grain dryers. The user accesses
the different programs by pressing switches 149 and 151 at the same
time. In response, the computer guides the user through the process
of selecting the proper program for the particular dryer 1 in which
the control circuitry of the present invention is installed. Note
that since the model of dryer is displayed in display 119 upon
startup, this feature allows the user or a technician to verify
that the proper software program for the particular model dryer
involved is enabled. The same input, actuation of switches 149,
151, allows the user to change the amount of time delay between the
starting of the fans, and allows the user to instruct the control
circuitry to ignore certain inputs such as the air pressure switch
inputs and the metering roll sensor inputs. Such operation might be
necessary in the event certain of these sensors fail, for example.
In addition, the computer is responsive to a predetermined input to
reset all timers to a preset amount. This allows a user who has
made a mistake in setting the timers to totally reset the system
readily and easily.
Note as well that the computer allows the viewing of timer and time
delay settings, the changing of these values, and the viewing of
the shutdown log on display 119 without interrupting dryer
operation. These tasks are handled simultaneously. The shutdown log
messages are specific so that the service technician or user knows
exactly which condition has shut down the dryer. An illustrative
list of such messages and their meaning is as follows:
"L1 Voltage Lost"--corresponding circuit breaker tripped or
hardware timer timed out
"12 Volt Power Supply Warning"--corresponding circuit breaker has
tripped
"Motor Overload"--thermal overload on a fan motor, load motor,
unload motor, or auxiliary motor has opened
"Burner 1 Vapor High Temperature"--sensor associated with that
burner has indicated that the temperature for that vapor is too
hot
"Burner 1 Warning Flame Not Detected"--flame sensor associated with
that burner has failed to detect a burner flame indicating that the
burner has failed to light, that there is a problem with the time
sensing circuitry, or that the dryer is not getting burner fuel
"Fan 1 Housing High Temperature"--temperature high limit sensor
located on the fan/burner housing has opened indicating an over
temperature condition has occurred towards the rear of the
fan/heater housing
"Grain Discharge Warning"--the cover of the grain discharge box has
opened indicating that grain is backing up into the discharge
box
"Lower Adj. Grain High Temperature"--an over temperature condition
has occurred inside the left side grain column
"Lower Fixed Grain High Temperature"--an over temperature condition
has occurred inside the right side grain column.
"Out of Grain--Unload Cleanout"--the dryer has run low on grain and
the out of grain timer has timed out, shutting the dryer down.
"Plenum 1 High Temperature"--an over temperature condition has
occurred inside the particular dryer plenum
"Meter Roll Drive System Failure"--the metering roll drive system
has failed to start turning, indicating a faulty d.c. motor, a
broken chain, or a jammed roll
"Right Metering Roll Failure"--the right metering roll has stopped
rotating or the sensor has been damaged
"Left Metering Roll Failure"--the left metering roll has stopped
rotating or the sensor has been damaged
"Auxiliary Safety Shutdown"--a shutdown has occurred due to a
user-installed safety feature.
"Burner 1 Shutdown--Loss of Airflow"--the air switch contacts have
opened indicating insufficient air flow for the corresponding
burner to operate.
"Fan 1 Failure--No Airflow"--the air switch contacts have opened
indicating the fan may not be turning.
"Fan 1 Cannot Start--Check Air Switch"--the air switch contacts
have closed prior to the fan starting, indicating a freewheeling
blade or improper setting of the air switch.
In addition to preventing any two fans from coming on at the same
time, computer 219 is programmed to prevent the possibility of any
two motors in general from being started at the same time. This
keeps peak current demands as low as possible.
The control circuitry, generally as heretofore described, is usable
with a multiplicity of combination grain dryers, as shown in FIGS.
1 and 2. For example, such a controller is used without
modification by Grain Systems, Inc., the assignee of the present
invention, to control over sixty (60) different models of such
grain dryers. Upon installing a controller in a dryer, the relevant
software for that model is enabled as described above. The proper
software thus programs computer 219 to control the proper number of
burners, fans, and sensors so as to properly operate the particular
dryer in which it is installed. By being able to use the same
computer controller on a wide number of grain dryers, inventory
problems during manufacture of the grain dryer are greatly reduced.
Likewise, in field servicing of the dryers, only a single
controller need be stocked as a replacement part for all such
dryers that possibly may need to be serviced.
Further, it will be understood that the computer controller of the
present invention may be used (as modified by software changes
only) to control grain dryers and other implements other than the
combination dryers above-described, as shown in FIGS. 1 and 2. For
example, the computer controller of the present invention may be
used to control a so-called batch bin dryer, as indicated in its
entirety at 301 in FIG. 22. Such batch bin dryers are commercially
available from Grain Systems, Inc. of Assumption, Ill., under the
trade designation "Top Dry" grain dryer. More particularly, batch
bin dryer 301 comprises a grain bin 303 having cylindrical
sidewalls 305 and a conical roof 305. A conical drying floor 307 is
mounted in the upper portion of the bin below roof 305. A conical
drying floor 307 is mounted in the upper portion of the bin below
roof 305. The drying floor has grain leveling shields 309 thereon.
The roof 305 had a center opening 311 through which wet grain to be
dried is loaded into dryer 301. The grain falls onto the apex of
the drying floor and flows down the sloped drying floor to form a
uniform layer of grain to be dried. Of course, the grain leveling
shields 309 insure that a uniform layer of grain to be dried is
formed on the upper face of the drying floor. This layer of grain
on the drying floor is analogous to grain column GC heretofore
described in regard to grain dryer 1. Drying floor 307 is of
perforate construction so as to allow heated air from below to flow
through the floor and through the grain supported on the floor for
drying the grain. The bin 301 has a fan/heater unit 49 (as
above-described) mounted on the bin sidewall 303 somewhat below the
conical grain drying floor. The fan/heater unit supplies heated air
under pressure into the interior of the grain bin beneath the
drying floor. The drying floor is provided with a plurality of
selectively operable doors 313 which when closed maintain the grain
of the upper surface of the drying floor and which when opened,
allow the dried grain to fall into the lower reaches of the bin
thus allowing another batch of set grain to be loaded on the drying
floor. The doors 313 thus constitute means for controlling the flow
of grain along the path of the grain as it is moved through batch
bin dryer 301. A number of sensors are located through the bin and
the fan/heater unit 49 to monitor various temperatures and other
conditions which indicate the status of the grain being dried. In
accordance with this invention, the controller of the present
invention, as above-described, may be used (as modified by suitable
software modifications as will be apparent to those skilled in the
art, especially in view of the above description of the controller)
to control and monitor operation of bin batch dryer 301, as above
described.
Still further, the computer controller of the present invention may
be used to control operation of conventional grain bin dryers using
a fan/heater assembly 49 to supply heated air into a plenum beneath
a perforated, horizontal drying floor in the bottom of the grain
bin and to control grain stirrers and the like. Also, the
controller may be used to control so-called tower grain dryers.
It should also be understood that the present invention is not
limited to a stand-alone grain dryer. The control circuitry of
dryer 1 may readily be connected through a suitable communications
channel 319 to a computer 321 disposed in the user's home or office
323 so that the user may monitor the grain dryer operation from
that remote location. Since computer 219 in the grain dryer has
stored therein all the switch positions and all triac and relay
closure information, that information is readily transmittable to
the home computer 321 for suitable display to the user. This
display is updated as the switches and triac/relay closures are
changed.
A typical display would be:
Unload Switch: 1 Speed
Metering Rolls: On
Unload Auger: On
RPM: 7.9
Bushels Per Hour: 990
Other information would include burner and fan status, etc.
The home computer 321 also monitors the safety circuit information.
Each time a safety shutdown occurs the problem, time, and date are
logged into the memory of computer 321. Note that the number of
safety shutdowns which computer 321 can record is not limited to
the twenty-five recordable by computer 219. If desired this
information can be printed out on a printer. In addition, a modem
can be used to communicate over telephone lines 325 so that the
shutdown information can be transferred to a remote site 327 such
as the factory where technical support is available. This enables
more rapid and accurate diagnosis of any problems with the
operation of the dryer. Of course, the modem could be actuated
automatically in the event of a shutdown, if desired.
In view of the above it will be seen that the various objects and
features of the present invention are achieved and other
advantageous results obtained. The description of the invention
contained herein is illustrative only and is not to be taken in a
limiting sense. The invention is limited only by the claims which
are appended hereto.
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